SCAR: Search Compile Assert Run

SCAR is a processor verification framework in python. SCAR performs a set of assembly level tests to verify the processor implementation. Each assembly test checks for one particular functionality of the processor. SCAR does this by examining a state dump file after the processor is done with executing a test code. This state dump file then checked assuming a set of assertions in the form of expected register values. These assertions are provided in the assembly file itself. SCAR is also used to verify the ISA-compliance.

SCAR Workflow

  1. Search: SCAR searches for all the available assembly level test in the directory and makes a list

  2. Compile: It then compiles all the found tests with a user-defined linker script.

  3. Execute: In this step, The elf files are executed on the target simulator which creates a state dump file after execution.

  4. Verify: Finally, Assertions are read from the assembly file containing the test. These are then used to check for mismatches in the generated state dump file.

Assembly test format

The assembly file must satisfy the following criteria:

  1. File must have a _start label before the start of code.

  2. File must have a ebreak instraction after the end of code.

  3. File must have an assertion section at the bottom with the following format.

Assertion Section Format

The assembly file must contain a set of assertions at the bottom in the following format:

 .global _start

li t0, 0x00d01010
li t1, 0x1ddc1044
li t2, 0xdeadbeef
li t3, 0x22101301
li t4, 0xfaf01569
li t5, 0x078b102a
li t6, 0xdae013c0

add a0, t0, t1
add a1, t1, t2
add a2, t2, t3
add a3, t3, t4
add a4, t4, t5
add a5, t5, t6


# eq a0 0x1eac2054
# eq a1 0xfc89cf33
# eq a2 0x00bdd1f0
# eq a3 0x1d00286a
# eq a4 0x027b2593
# eq a5 0xe26b23ea

State-Dump file format